Risk of Malaria in the Presence of Sickle Cell Trait and Alpha Thalassaemia
Two blood disorders, sickle cell trait and alpha thalassaemia, are individually associated with a decreased risk of malaria. Scientists have found, however, that people with both genetic disorders are no longer protected against malaria.
People who carry one copy of the point mutation in the hemoglobin beta gene (HBB) on chromosome 11p15.4 experience sickle cell trait and a reduced risk of malaria. Carriers of two copies are affected with sickle cell anemia, characterized by episodes of pain, chronic hemolytic anemia and severe infections, usually beginning in early childhood.
In alpha thalassemia, the hemoglobin which carries oxygen in the body lacks the alpha polypeptide chain component resulting in a low concentration of oxygen in tissues. Deletions in either the HBA1 or HBA2 hemoglobin alpha genes cause most cases of alpha thalassemia.
Researchers had expected to find an additive effect leading to an even greater level of protection from malaria. Lead researcher Dr Tom Williams said:
Our study shows that it can be very complicated to turn up genetic associations and properly understand them. If one trait can interfere with the effects of another, you may miss an association where one truly exists. Conversely, you may find a trait that seems to provide protection but not see how other traits could alter the effect.
The mind boggles at the complex, multi-layered, multi-dimensional interactions between genes (not to mention environment!).
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POSTED IN: Genetics of Disease
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